PROBLEM QUESTIONS 143 



(a) Crustacea. Limy skeleton, segmented, body divided into 

 two regions, more than three pairs of walking appendages, breathe 

 through gills. Examples: crayfish, crab, lobster. 



(b) Insecta. Having a horny skeleton (chitin), only three 

 pairs of walking legs, breathe through tracheae. Examples : bee, 

 ant, grasshopper. Two smaller groups of Arthropods are also 

 found : the Arachnids, spiders, having four pairs of legs, and the 

 Myriapods, " thousand leggers," which have many pairs of simi- 

 lar jointed legs. (Page 185, Civic Biology.) 



g. Mollusks 



Examples : clam, snail, oyster. Have a soft, unjointed body, 

 usually covered with a hard limy shell of one or two pieces (valves) . 

 This shell is formed by a covering called the mantle. These ani- 

 mals breathe through gills. (Page 185, Civic Biology.) 



h. Vertebrates 



Examples : fish, frog, turtle, bird, dog. Having an internal limy 

 skeleton composed of pieces of bone jointed together. Also an 

 external skeleton which may be scales, bone, feathers, nails, or 

 hair. Breathe by gills or lungs. Central nervous system on back 

 or dorsal side of body protected by a chain of bones called the 

 vertebral column. (Pages 185-192, Civic Biology.) 



Method and Observations. Using the above directions pick 

 out of the material given you one specimen of each group and 

 arrange the specimens selected in a series showing evolutionary 

 order. 



Conclusion. 1. What do you mean by evolutionary order? 



2. Has division of labor anything to do with your placing these 

 specimens as you have? 



PROBLEM QUESTIONS 



1. Why do we speak of the plant or animal kingdom? 



2. What results from fertilization in both plants and animals? 



3. How are egg cells protected in birds? In a flower? Why 

 should they be protected? 



